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50% dod outdated
#1
So ive been boondocking 4.5 months in a new to me class c. I been fixing it up and in the mean time havent put a proper set of cabin batteries in yet. It has a group 24 everstart right now. Date coded 8/17.

I got 200w of solar with a renogy rover 20a set to basic FLD parameters and a oem magnatek converter.

Now in my old rig ive always ran 250w solar syatem with 2 GC2 duracells and an ecoworthy clone set on user with charge para.eters bumped .2v.

This class c with a group 24 starting battery has been more usable and less frustrating by far than my old one ever was. I do not want for power as i use generator 30 minutes anyway to brew coffee. Sunny days do not need it. I run 20" tv and phone charge to 1am every night. Its also running pumps and lights intermittently. It keeps up just fine albeit i drop it to 30-40% cause i do not plan on keeping it anyway.

So i got wondering are we killing batteries by over building the bank size and only allowing 50% discharge?  Id wager the vast majority running on solar sulfate batteries long before they short a cell. I know thats been the case in my old rig for the past 3 sets. Even with 14.8v set absorption. Maybe we should start building banks for a 70% discharge rate to help keep the sulfation down since were killing them early anyway.

Thoughts?
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#2
not qualified to speak on cycling but efficiency could be a part of why your new rig system works better than the old,wire size and quality,device power usage...just switching to led lights make a good difference
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#3
I've also gone way down in battery capacity. I can fit a max of 2 group 27s under body, and one group 31 in engine compartment. Everything's wired up for such a system, but Since June 2015 i have been using a single group 27 Northstar AGM(90Ah, 930CCA) for both house and engine starting.
I regularly discharge well below 50%, and this battery has had No issues starting my engine in mild ambient temps when discharged to these low levels.

But, All my charging sources are voltage optimized, and I can and do plug in if too much low and slow solar and perhaps not enough of that, has been occurring too many days in a row. Plugging in and paralleling chargers, I can get 65 amps, alternator about 106 charging amps with enough rpm, Solar 11.5 amps and with portable panels, can double that.

I deliberately lowered capacity, but in stages. I went from 2 group 27's in parallel to one group 31 as a house bank specifically to be able to achieve a higher charge rate via solar alone, and the $ per cycle and total KWH passed was improved, and when that screwy31 was too worn out, I started Cycling my AGM-27 while I was modifying the engine battery comprtment to accept a taller Trojan T-1275 or similar GC-15 size group, the only true deep cycle flooded 12v battery, but then realized I do not even need a house battery.

My AGM appears to love high charge rates from a low state of charge. if I had two of them I would not be able to achieve these really high charge rates. When it appears lazy I deliberately deplete it farther than I normally would, just to be able to apply high amperage for a long time until 14.7v is reached then hold 14.7v until amps taper to a very low level.

I think(opinion) this high amperage every so often helps redissolve and prevent hardened sulfation on all lead acid batteries, though we always hear/read about how much better a low charging rate is for the battery. Horse hockey in my opinion, when actually regularly deep cycling said battery in vehicular usage. if in a golfcart plugged in in the evening, size the charger to be able to reach full before the next possible usage 10 to 12 hours away, but Vehicle dwellers should be aiming for maximum charge rate anytime they can be charging, plugged in or driving, and the solar sized to be able to reach absorption voltage no later than 1PM on a good sunny day and preferably much earlier.

Obviously there are benefits to having lots of battery capacity, but for me more capacity proved unneeded, and false confidence for weak bragging rights, as my battery life with more capacity was poor, and my van had to carry around 60 to 120 more Lbs just for that lesser lifespan.

I'd not be so brave as to intentionally start deep cycling a single wally world valuepower 55$ group 24 starter battery though.

But perhaps total KWH the battery provided per $, could make it a good investment for some.

My Northstar AGM is old enough and has so many deep cycles on it, I recently got a cheap 18Ah AGM jump starter battery just for peace of mind should the Northstar decide that it has had enough and not be able to start my engine. I guess the same strategy can be employed with the valuepower battery. Can go through ~5 of those before reaching the cost of one Northstar AGM-27.

But I'd prefer one Northstar AGM vs 5 valuepower flooded 24's back to back.

I do think the 50% 'rule' for lead acid is a bit asinine in most uses, but if it takes several days to depletee to 50% with no solar or significant recharging occurring, then one should not take a few more days to get to 20% State of charge. If recharging to full can occur the next day, then take it to 20% the night before, if one needs to. Cumulative cycles back to back without being able to reach 100% is the battery killer. Regular true 100% recharges are the battery life extender.

One thing with having way more capacity, well if the alternator is told to seek and hold high voltages by the voltage regulation, then a lot of battery capacity can overheat the alternator. If it is internally voltage regulated and a thermal regulator that lowers voltage once the laternator is hot, then the lower the voltage the slower the batery recharging is.

My Single Northstar is very amperage greedy when depleted, and can max out the alternator, but only for so long before it reaches 14.7v and amps begine to taper. If I had more battery capacity it would take higher amperage for even longer and perhaps be able to overheat and prematurely kill the alternator, at the most inconvenient and dangerous time for it to decide to do so.

Before I got solar I was replacing 'lifetime' warranty alternator replacements quite often, cycling those 2 or 3 group 27 batteries.

Now I can command what voltage my alternator is told to seek, and can almost always recharge the single 90AH battery as fast as possible whenever i drive( except idling at redlights). if I had more battery capacity I could not achieve this, and in my Mind it is hardened fact that this Northstar AGM has a life extending orgasm every time I feed it 40+ amps from a well depleted state. Voltage retention the next several disharges after ahigh amp blast batterygasm is much improved, long after the warmer battery that first discharge cycle imparts.

Thin plate flooded starting batteries are designed to deliver high cranking amps, via thin porous plates and the inherent low resistance. This low resistance means they can be recharged quickly, at least to teh 80 to 85% charged range quickly too.

I'm not willing to prove or disprove the validity of cheap starting batteries in deep cycle duties but i do believe the 50% rule is a bit Whack, and that carrying too much battery capacity can be detrimental to that battery capacity especially when the charging sources cant really truly fully charge them on a regular basis.

Actual deep cycle flooded batteries, like GC-2s, when sulfated, can have much capacity returned by a full charge followed by an Equalization charge. They can tolerate many of these abusive capacity restoring Equalization charges, bringing the battery as high as 16.2v for as long as required to maximize specific gravity. I doubt the thin plate starting battery can handle many of these EQ charges.

But if one does not have the ability , equipment, or understanding/desire to actually perform a life extending EQ charge wen the sulfation is beginning to harden, then the deep cycle batteries capacity can appear to be a lot of useless weight in short order too.
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#4
I must disagree. I used to build remote cabin power systems & the only solar was 1 panel to keep the batteries charged over long spells of no one being there. 6 flooded 6v GC batts, A roll around charger, a 2000 watt inverter, an automatic switch that when the genset started it dave 1 minute before switxhing rom the invertor to the genset, onan 2500 watt genset all in a outhouse looking building. I was so quiet you had to perfectly quiet to hear it start. Onans have automatic chokes & run at 1800 rpms. We;d start the genset from inside the cabin & make a pot of dtip coffee every morning about 20 minutes & that was all we needed. I had a iltmeter in the cain by the on/off/start switch. We had all the power for the day & never drained the batteries very low. I didseveral setups for friends & lways got at leaast 12 years  on a set of batteries. The secret is not to deep discharge the batteries. Just what worked for me YMMV.

 I found a solar panel factory I can buy 320 watt cosmetic blems for $50 & not sure if I even need them as the ambo has a 250 amp altenator & am doing the diode mod that adds .6 volts to the charge.
Let me recommend the best medicine in the world, a long journey, at a mild season, through a pleasant country, in easy stages. James Madison


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#5
Huh   My head hurts after that last post. 

Dodgy   I had a flashback of the reason why I left the other board.  Sad Sad
Compared to parenting, Cat herding is less complicated 
[-] The following 2 users say Thank You to GotSmart for this post:
  • Wayne49 (04-14-2019), Matlock (04-16-2019)
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#6
(04-13-2019, 06:20 AM)Ddarnell Wrote: So ive been boondocking 4.5 months in a new to me class c. I been fixing it up and in the mean time havent put a proper set of cabin batteries in yet. It has a group 24 everstart right now. Date coded 8/17.

I got 200w of solar with a renogy rover 20a set to basic FLD parameters and a oem magnatek converter.

Now in my old rig ive always ran 250w solar syatem with 2 GC2 duracells and an ecoworthy clone set on user with charge para.eters bumped .2v.

This class c with a group 24 starting battery has been more usable and less frustrating by far than my old one ever was. I do not want for power as i use generator 30 minutes anyway to brew coffee. Sunny days do not need it. I run 20" tv and phone charge to 1am every night. Its also running pumps and lights intermittently. It keeps up just fine albeit i drop it to 30-40% cause i do not plan on keeping it anyway.

So i got wondering are we killing batteries by over building the bank size and only allowing 50% discharge?  Id wager the vast majority running on solar sulfate batteries long before they short a cell. I know thats been the case in my old rig for the past 3 sets. Even with 14.8v set absorption. Maybe we should start building banks for a 70% discharge rate to help keep the sulfation down since were killing them early anyway.

Thoughts?
Very interesting but I am too new to converse intelligently about solar.

Sent from my moto z3 using Tapatalk
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#7
Don't know why an offgrid house is brought into this discussion, Pretty much unlimited space in which to house battery banks, solar panels and generators. Not really comparable to a vehicle which must carry everything.


Quote: Id wager the vast majority running on solar sulfate batteries long before they short a cell. I know thats been the case in my old rig for the past 3 sets. Even with 14.8v set absorption. Maybe we should start building banks for a 70% discharge rate to help keep the sulfation down since were killing them early anyway.

The key statement in this paragraph is 'even with a 14.8v absorption.'

The DURATION at which absorption voltage is held, is more important than a few tenths of a volt.

I mean I could apply 150 amps and instantly get a single 50% charged battery to 14.8v. Does this mean the battery is fully charged, and immune to beginnings of sulfation? Of course not. Still going to take no less than 4.5 hours at 14.8v even with 150 amps applied initially to achieve that 14.8v.

2 hours held at 14.8v is better than 2 hours at 14.6 on a deeply dischared battery, but 3 hours of 14.6v is better than 2 hours of 14.8v. Some seem to think that a trojan battery, that specs a 14.82v avsorption set point, is imposssible to recharge fully at any less of an absorption voltage. This is Not true at all. 14.82 will charge faster than 14.6v of course, and cause more water usage, but 14.6v can still complete the task on a still otherwise healthy battery, it just takes longer. Will there be enough time in the day to do so, well 14.82 will stand a better chance of that certainly, should the charge controller allow for that extra duration.

Battery manufacturer recommended voltages have to consider how they believe the majority of their batteries are going to be used, and what recommendations will lead to the least possible number of warranty returns, yet also yield an acceptable life beyond the warranty to develop a reputation. Basically they are second guessing the end user and like everything it comes down to max profit for the fat cat cigar smokers at the top.

i am not saying ignore the manufacturer recommended voltage settings for their batteries, but to understand why they set them where they do. A while back Trojan upped their recommended equalization voltage from 15.5 to 16.2v. Did they do this because they changed the make up of the plates, or because they found that 45 minutes of 16.2v was more effective at maximizing specific gravity and less damaging to those plates than 2 hours of 15.5v? OR did they do it simply because Rolls Surrette has always recommended 16.2v and RS is the Bigwig on the deep cycle flooded battery world?

The 'trick' is to hold absorption voltage long enough so that the battery does reach a true full state of charge, and the more often this happens the longer the battrey will lasty, even with depth of discharges below 50%.

But the deeper the discharges the more important it is to actually reach a true full charge. Lesser depth of discharges are not as damaged by not quite reaching full day after day.

So if one is sulfating batteries prematurely, or what they believe to be so, are they actually checking specific gravity of the flooded cells when their absorption stage is done, or noticing the amperage while the battery is still held at absorption voltage?

The TIME/DURATION as to how long to hold the lead acid battery in absorption is so often overlooked, in favor of the actual absorption voltge number. The time needed in absorption will increase as the battery ages, increase with the depth of discharge, increase with lesser battery temperature, and if only 2 hours at 14.7v absorption are allowed and the battery needs 4.5 hours, guess what, the sulfation destroys the available capacity.

so have all the faith you want in your charge contrller/charging sources ability to fully charge the battery, keep in mind it has NO IDEA the actual state of charge of the battery. the green light indicating full charge is mocking the human who believes it.

Confirm true full charge with a hydrometer, or if with AGM batteries , an Ammeter. 95% of the time the person who seeks to confirm full charge or a marginally or deeply cycled battery, by either method, will find the batteries NOT fully charged, and be stuck with a charging source that inisits that they are, and holds a piddly float voltage at which almost no charging occurs. 1/3 to 1/2 the amps will actually flow into a battery at almost any state of charge, at 13.7 vs 14.7v, and if one is using a 13.2v flooded setting the actual charging occuring is dismally low, and 48 hours of 13.2v will not be able to do what 45 minutes more of 14.7v could have had it been allowed to continue.

Hoping that a float voltage will have enough time to actually fully charge a battery bank before sundown is unwise in the extreme, again proveable by anybody who does not have faith in their product's marketing, and seeks to confirm using a hydrometer or an ammeter with the battery at absorption voltage.

The ability to reach a true full state of charge often and regularly can allow one to dismiss the 50% 'rule'. I am not saying size the battery bank to run it down to 20% each night, just don;t believe that going to 49% state of charge means instant death. it is much easier to kill a battery prematurely by allowing only 2 hours of absorption, when 3.5 are required to reach full charge.

And it is far far more likely 3.5 hours are required on a deeply cycled battery.

Shallow cycling of larger battery banks has different requirements, absorption need not be held nearly as long, and the stock configurations of minimal solar wattage feeding a large minorly depleted battery bank, might be 'just fine'.

I've gone the high battery capacity route with minimal solar, and achieved horrendous battery life, and my van had to carry around an extra 120Lbs of prematurely sulfating battery. No way would I go back to that or recommend others do so on a wheeled platform. Offgridstickandbrickhomessolar.com , do whatever.

Just verify you can achieve and hold absorption voltage for long enough, to regularly be able to achieve a true full charge.
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#8
(04-13-2019, 06:20 AM)Ddarnell Wrote: So ive been boondocking 4.5 months in a new to me class c. I been fixing it up and in the mean time havent put a proper set of cabin batteries in yet. It has a group 24 everstart right now. Date coded 8/17.

I got 200w of solar with a renogy rover 20a set to basic FLD parameters and a oem magnatek converter.

Now in my old rig ive always ran 250w solar syatem with 2 GC2 duracells and an ecoworthy clone set on user with charge para.eters bumped .2v.

This class c with a group 24 starting battery has been more usable and less frustrating by far than my old one ever was. I do not want for power as i use generator 30 minutes anyway to brew coffee. Sunny days do not need it. I run 20" tv and phone charge to 1am every night. Its also running pumps and lights intermittently. It keeps up just fine albeit i drop it to 30-40% cause i do not plan on keeping it anyway.

So i got wondering are we killing batteries by over building the bank size and only allowing 50% discharge?  Id wager the vast majority running on solar sulfate batteries long before they short a cell. I know thats been the case in my old rig for the past 3 sets. Even with 14.8v set absorption. Maybe we should start building banks for a 70% discharge rate to help keep the sulfation down since were killing them early anyway.

I posted a place with all the info you'll need on batteries but either you missed or ignored it. https://batteryuniversity.com/learn/
Let me recommend the best medicine in the world, a long journey, at a mild season, through a pleasant country, in easy stages. James Madison


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#9
Well if time on absorb means more than a voltage bump, which to me is obviously true, what controllers actually hold absorption long enough?

Cause Ive had all the chinese MPPT's and none of them seem to be up to muster. Are we talking about the original name brands at $400? (Morningstar, outback, etc) what say ye on victrons?
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#10
I spent prob $130ish on a 20a tracer type charge controller that came with a remote meter to program it. It's working good enough for me. Something like in the link, except I bought the metal heavy duty charge controller. I am not recommending what's in the link, just for showing you.

https://www.amazon.com/ACOPOWER-Solar-Ch...way&sr=8-6
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